The following invention relates to a multi-additive injection system primarily for aviation fuel. More particularly, though not exclusively, the invention relates to the real-time addition of additives in correct proportions both before and after a fuel filter in a hydrant servicer cart for use at airports. In more general terms, the present invention relates to a system designed to inject aviation fuel additives in the main jet fuel stream on aircraft refuelling hydrant carts, self-powered hydrant carts or aircraft refuelling tankers. By injecting in-line and close to the aircraft, additive losses in storage and distribution are minimised. Consequently, reduced concentrations of additives can be considered.
Commercial aircraft for example require standard aviation fuel that is available from pressurised underground mains accessed by hydrants at the loading/unloading aprons of airports.
Some aircraft, such as military aircraft, require a special blend of fuel that is not available at most commercial airports. Therefore, such aircraft must return to military airbases for refuelling. In situations such as wartime, this poses serious limitations on military strategics.
It is known to provide hydrant servicer carts at commercial airports which can remain on the apron at a particular bay while being readily movable from one side of an aircraft to the other. Such carts often include a refuelling platform for supporting an aircraft refuelling person or persons, the platform being capable of being raised to a refuelling position at the wing or fuselage of the aircraft. Such carts have a hydrant hose having a coupler for connection to an airport fuel hydrant, a fuel conveying boom which receives fuel from the hydrant hose, the boom being vertically extendible and retractable and capable of conveying the fuel. A fuel hose is coupled to an upper end of the boom and receives fuel from the boom for delivery to the aircraft. A fuel filter is often provided on such carts to ensure that the aircraft receives properly filtered fuel.
It would be extremely beneficial if such carts could be provided with means for providing controlled-dosage real-time addition of a plurality of fuel additives during a refuelling operation. This would enable military aircraft for example to be refuelled at commercial airports provided with such carts. Such carts would include a storage vessel for each fuel additive or a multi-compartment vessel containing all of the required additives in appropriately sized compartments.
It might also be desirable to provide a means of real-time injection of additives to a flow of liquid such as fuel. Such a flow of liquid might be the flow of fuel to a storage tank.
It would further be desirable to provide a multi-additive injection means for a fuel line wherein the supply of individual additives can be independently controlled and even turned off, for example, when other additives are still being injected.
It would also be desirable to provide a monitoring process for each additive simultaneously while fuel is flowing in the main stream. A computer system might monitor each additive and record the amounts and calculate the percentage concentration of each additive according to pre-programmed data and record the results.
It is the object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages and/or more generally to provide a multi-additive injection system, typically for aviation fuel and preferably providing one or more of the above advantages.
There is disclosed herein a multi-additive injection system for injecting required amounts of different additives to flowing fuel in a fuel line, the system comprising:
a plurality of additive injection sub-systems, each sub-system comprising:
a source of additive,
a pump to deliver additive from said source to said fuel line,
additive metering means to measure an amount of said additive being delivered to said fuel line by said pump,
said multi-additive injection system further comprising:
fuel metering means to measure an amount of fuel flowing through said fuel line, and
control means responsive to said additive metering means and said fuel metering means to control said pump of each sub-system to adjust said amount of additive being delivered by each said pump, should an amount of additive metered by said additive metering means deviate from a predetermined amount.
Preferably each additive sub-system delivers its respective additive to said fuel line at a different position along said fuel line.
Preferably said fuel line has in-line therewith a fuel filter.
Preferably one or more of said additives is added up-stream of said filter and one or more of said additives is added to the fuel line down-stream of said filter.
Preferably said additive metering means monitors mass and percentage concentration of said additive in relation to the flow rate of fuel in the fuel line.
Preferably said additive metering means and fuel metering means act simultaneously while fuel is flowing through said fuel line.
Typically, the quantity of each additive injected into the jet fuel as measured by the flow meters will be reconciled against measurements of the amount of additive in the storage tanks to provide failsafe quality assurance. Additive volumes in the storage tanks can be calculated by level measurements or load cells.
Preferably said additive metering means and fuel metering means comprise a computer system which records the respective amounts and calculates the percentage concentration of each additive according to pre-programmed data.
Preferably said computer also acts as said control means.
Preferably each said source of additive comprises an additive tank.
Preferably each additive tank includes means for reading the level of additive therein.
Preferably said computer continuously audits the levels of additive in each tank during operation.
Preferably said computer records said levels of additive.
Preferably four additive injection sub-systems are provided, one for an anti-icing additive, another for a thermal stability improver additive, another for a corrosion inhibiter/lubricity enhancer additive and another for a static dissipater additive.
Preferably the computer compares the flow rate of fuel within the fuel line with the flow rate of additive delivered by each additive injection sub-system to the fuel line so as to calculate a percentage concentration of each additive in the fuel within the fuel line.
Preferably if said percentage concentration cannot be kept within a pre-determined minimum and maximum level, the computer system will shut down the refuelling operation.
Preferably said fuel metering means comprises a mass flow meter.
Preferably said additive metering means comprise mass flow meters.
Preferably each fuel additive tank is sized according to the quantity of fuel required in a particular refuelling operation, each tank being fitted with an electronic level gauge, air vent and quick-disconnect suction line.
Preferably each tank is manufactured from a material compatible with the additive intended to be stored therein.
Alternatively, each additive tank can be a container in which the additive is purchased and suction fittings can be supplied to accommodate the container.
In such instances, the quantity of additive in each tank can be monitored by a load cell or cells under each tank.
For fuel additives that are hydroscopic, the tank can be provided with a silica gel crystal air vent to absorb water from the air.
As an alternative, each additive tank can be formed as a discrete compartment within a unitary structure. Appropriate suction connections can be fitted to suction ports provided at each compartment.
Each compartment can be provided with an air vent connected to a common manifold. Preferably the manifold can be fitted with a silica gel crystal air vent to absorb water from the air.
Preferably the unitary structure can be provided with fork lift pockets to enable a fork lift truck to handle the structure.
Preferably the pump for each additive is a metering type pump unit.
Preferably the metering type pump unit has adjustable pump stroke and motor speed.
Preferably each additive pump is fitted with a double-diaphragm leak detection system.
Preferably each additive injection sub-system comprises a suction isolation valve, a suction strainer, a suction shut-off valve, a suction pressure gauge with isolation valve, a metering pump, a discharge pressure gauge with isolation valve, a relief valve piped back to the source of additive, a discharge shut-off valve and a pulsation dampener with isolation valve and drain valve back to the additive source.
Preferably the computer system will be capable of printing out a transaction ticket showing the following:
total amount of fuel having passed through the fuel line.
total amount of each additive loaded in kilograms or pounds.
flight details.
aircraft serial number or flight number.
date and time.
Preferably the computer system will transmit the above data to a control office main frame computer or desktop computer to process information.
There is further disclosed herein a hydrant servicer cart for use in refuelling aircraft, the hydrant servicer cart including a fuel line for receiving fuel from pressurised underground mains and for delivering the fuel to an aircraft, the fuel line having in-line therewith a fuel filter, the fuel line having connected thereto a multi-additive injection system for injecting required amounts of different additives to flowing fuel in said fuel line, the multi-additive system comprising:
a plurality of additive injection sub-systems, each sub-system comprising:
a source of additive,
a pump to deliver additive from said source to said fuel line,
additive metering means to measure an amount of said additive being delivered to said fuel line by said pump,
said multi-additive injection system further comprising:
fuel metering means to measure an amount of fuel flowing through said fuel line, and
control means responsive to said additive metering means and said fuel metering means to control said pump of each sub-system to adjust said amount of additive being delivered by each said pump, should an amount of additive metered by said additive metering means deviate from a predetermined amount, and wherein one or more of said additives is added to the fuel line downstream of said filter.